Selective hydrodeoxygenation of lignin phenolics to cyclohexanols over low-Ru catalysts

Abstract

The selective conversion of lignin-derived phenolics into cyclohexanols through demethoxylation and ring hydrogenation, while preserving hydroxyl groups, remains a significant catalytic challenge but offers a green alternative to fossil resources. Here, we report a low-loaded Ru catalyst supported on Al2O3 (Ru0.36CN/γ-Al2O3) that enables the efficient production of cyclohexanols from lignin-derived phenolics in water. Under optimal conditions, 4-propylguaiacol is converted to 4-propylcyclohexanol in 77% yield. The catalyst also exhibits excellent recyclability and broad substrate scope. A plausible reaction pathway is proposed based on detailed studies of intermediate compounds. Moreover, lignin-derived bio-oil obtained from the reductive catalytic fractionation (RCF) of Chinese fir is upgraded to alkyl cyclohexanols with a yield of 23.2 wt% and selectivity of 69.5%. This work highlights the potential of low-loaded Ru catalysts for the sustainable production of cyclohexanols from lignin-derived feedstocks.